Meeting Abstract

65.2  Sunday, Jan. 6  Placental ontogeny of two species of biennially reproducing snow skinks (Scincidae: Niveoscincus) STEWART, J. R.*; THOMPSON, M. B.; East Tennessee State University; University of Sydney stewarjr@etsu.edu

Viviparity and placentation have evolved in numerous lineages of squamate reptiles, yet only five of these are substantially placentotrophic. One of these lineages, the scincid lizard genus Niveoscincus, is geographically distributed in cool, mesic habitats of southeastern Australia, with six of the eight species endemic to the island state of Tasmania. Previous work on three species, N. coventryi, N. metallicus and N. ocellatus, has revealed that the level of placentotrophy is correlated with placental structural complexity. All three species have both a chorioallantoic placenta and an omphaloplacenta (yolk sac placenta). Structural differences between the two predominantly lecithotrophic species, N. coventryi and N. metallicus, and the highly placentotrophic N. ocellatus, include more extensive distribution of interdigitating ridges in the chorioallantoic placenta and complex folding of the embryonic component of the omphaloplacenta in N. ocellatus. A recent phylogenetic analysis places N. coventryi and N. metallicus basal to N. ocellatus and also suggests close affinities between N. ocellatus and two biennially reproducing species, N. greeni and N. microlepidotus. We used light microscopy to study placental ontogeny and morphology of N. greeni and N. microlepidotus and conclude that the placentae of these two species are indistinguishable and share more characteristics with N. ocellatus than they do with either N. coventryi or N. metallicus.